The synthesis of polyureas by the polyaddition reaction of diisocyanates or polyisocyanates with amines in the absence of solvents frequently presents difficulties. One reason for this lies in the high reactivity of the starting materials, which frequently react with one another readily upon being mixed. However, good mixing is a prerequisite for achieving a uniform reaction. Such mixing becomes difficult when, because of different equivalent weights, the volumes to be mixed are different and/or the viscosity of one of the reactants is relatively high. If the functionality of the reactants is high, so that the reaction results in highly viscous or solid products with high cross linking densities, the further processing of the reaction mixture and/or the dissipation of the heat of reaction is difficult. In every case, the starting materials must be stored separately and can be mixed only immediately before they are reacted with one another.
Similar problems arise with the solvent-free synthesis of polyurethanes from diisocyanates or polyisocyanates and glycols or polyols, such as polyetherols or polyesterols.
During the synthesis of molded polyurea or polyurethane objects by the casting method, these difficulties can lead to inhomogeneities due to different temperatures between the edge phase and the core, to the formation of bubbles and cracks due to overheating in the interior, to insufficient bonding of soft and hard segments due to the great differences in the reactivities of individual components and to side reactions and decomposition reactions.
It is also possible to carry out the reaction of the isocyanates with the polyethers, polyesters, polyamine or similar reactive compounds with active hydrogen atoms directly in the injection molding machine, in a reaction kneader or in a reaction extruder. If the viscosities of the reactants and/or of the polymers formed are high, metering out, mixing and transporting the reacting mixture or the polymers obtained create difficulties or make the use of this method impossible.
The present invention is concerned with the technical problem of the solvent-free synthesis of such polyaddition products with avoidance of the aforementioned difficulties. More particularly, it is concerned with the problem of metering out and mixing the starting materials uniformly and with reacting the starting materials, which frequently react spontaneously, in a controlled manner with one another. In this manner, homogeneous products are obtained, while temperature, which can cause side reactions or decomposition reactions is avoided. These mixtures of the reactants can be stored without any reactions worth mentioning taking place among the reactants.